With the inception of the tractor-trailer vehicles the tractor vehicle was relatively low to the ground as compared with the trailer unit which was high and boxy to include as much volume as the law would permit for the carrying of cargo. As a result, the air flow impinging on the trailer at high speeds exerts a high degree of force, particularly if a strong head wind existed. This coupled with long down hill grades is proving to be a dangerous situation because more braking effort is now required to slow down or stop these vehicles than was required before these improvements were made.
1. Field of the Invention
Broadly stated this invention pertains to the control and deflection of the passing air flowing over and around the tractor-trailer vehicle to cause it to flow over and around the trailer with the least degree of deflection and resistance at road speeds. As soon as the brakes of the vehicle are applied the air deflecting doors open up, and the inlet doors open to deflect and redirect the air to impinge on the substantially flat front surface of the trailer vehicle to increase the resistance applied by the brakes by slowing down the vehicle. This imposes a substantial resistance on the trailer vehicles forward momentum thereby increasing the braking effect that must be applied to control the speed of the vehicle at the higher road speeds.
2. DESCRIPTION OF THE RELATED ART
Efforts have been made to utilize the air flow striking the trailer unit to reduce the speed of the rig. One of the early developments seeking to reduce the braking force required is Stamm U.S. Pat. No. 2,863,695 of 1958 in which an effort was made to deflect and guide the air flow from the tractor unit to the trailer unit to change its course and direct air to flow to the trailer mounted element 40 on top of the trailer. This effort was more theoretical than practical because of the long vertical step, as seen in FIG. 1, between the top of the cab on the tractor vehicle to the top of the trailer unit, a distance that was entirely too high to be accomplished in the short horizontal distance available.
Peairs U.S. Pat. No. 4,607,874 of 1986 had a shield 10 mounted transversely of the top of the tractor cab which could be moved angularly depending on the speed at which the vehicle is driven to deflect the air flow to project it over the top of the trailer 14 to reduce the resistance involved.